This invention relates to a diagnostic system and non-intrusive method of detecting internal defects in moving devices such as rotating and oscillating apparatus.
Rotary compressors used in room air conditioners have exceptionally light tolerances, in some cases only a few ten-thousandths of an inch. In addition they are hermetically sealed and therefore prone to early failure if small particles are present or introduced during assembly. When the compressor contains clean, correctly dimensioned parts and is properly assembled, normal noises are generated internally. Changes in these sounds indicate that the compressor is abnormal.
Some of these defects can be found by a trained operator but are subject to human interpretation. The pass-fail criteria vary between operators and also from day to day with the same operator. Some of the defects cannot be found by any operator. It was impossible to discover some small particles of hardened material that shorten life.
The warranty period for a compressor is five years and it is expensive to repair in the field. This invention is more sensitive than a human operator and the acceptance criteria are consistent. It is capable of performing an inspection at one test station that would require more than one station using more conventional methods.